Comparison of the equilibrium, kinetic and water exchange properties of some metal ion-DOTA and DOTA-bis(amide) complexes.

The 1,7-diacetate-4,10-diacetamide substituted 1,4,7,10-tetraazacyclododecane structural unit is common to several responsive Magnetic Resonance Imaging (MRI) contrast agents (CAs). While some of these complexes (agents capable of sensing fluctuations in Zn, Ca etc. ions) have already been tested in vivo, the detailed physico-chemical characterization of such ligands have not been fully studied.

Synthesis and characterization of a hypoxia-sensitive MRI probe.

Tissue hypoxia occurs in pathologic conditions, such as cancer, ischemic heart disease and stroke when oxygen demand is greater than oxygen supply. An imaging method that can differentiate hypoxic versus normoxic tissue could have an immediate impact on therapy choices. In this work, the gadolinium(III) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) with a 2-nitroimidazole attached to one carboxyl group via an amide linkage was prepared, characterized and tested as a hypoxia-sensitive MRI agent.

Lanthanide(III) complexes of tris(amide) PCTA derivatives as potential bimodal magnetic resonance and optical imaging agents.

Lanthanide complexes of two tris(amide) derivatives of PCTA were synthesized and characterized. The relaxometric and luminescence properties of their lanthanide complexes were investigated as bimodal magnetic resonance (MR) and optical imaging agents. Luminescence studies show that one of the Tb(III) complexes dimerizes in solution at low millimolar concentrations, whereas the other may have a higher than expected coordination number in solution.

(S)-5-(p-nitrobenzyl)-PCTA, a promising bifunctional ligand with advantageous metal ion complexation kinetics.

A bifunctional version of PCTA (3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid) that exhibits fast complexation kinetics with the trivalent lanthanide(III) ions was synthesized in reasonable yields starting from N,N',N''-tristosyl-(S)-2-(p-nitrobenzyl)-diethylenetriamine.

Synthesis and Characterization of DOTA-(amide)(4) Derivatives: Equilibrium and Kinetic Behavior of Their Lanthanide(III) Complexes.

Lanthanide complexes of tetraamide derivatives of DOTA are of interest today because of their application as chemical exchange saturation transfer (CEST) agents for magnetic resonance imaging (MRI). The protonation constants of some simple tetraamide derivatives of DOTA and the stability constants of the complexes formed with some endogenous metal ions, namely Mg(2+), Ca(2+), Cu(2+), Zn(2+), and lanthanide(III) ions, have been studied. These complexes were found to be considerably less stable than the corresponding [M(DOTA)](2-) complexes, largely due to the lower basicity of the tetraamide ligands.